Some of the presently known brake cylinder devices include, in addition to actuating piston means for providing service and emergency braking forces, parking brake means by which the brake cylinder, subsequently to having brought the vehicle to a stop, may be activated for locking the actuating piston in a brake-applied position and thus maintaining the brake shoe against the braking surface, such as the tread of a wheel. Since a vehicle wheel, especially a railway vehicle wheel, undergoes thermal expansion during braking, there is an attendant corresponding shrinkage as the wheel cools. This results in a tendency to reduce locked-up tension of the brake components and, thereby, a loss in parking brake effectiveness.